U818A HD Carryability

[LoneRCRanger]

I was wondering how much weight my U818A HD is able to lift and carry in a sustained flight? My thought on this is to add a liftable weight to help stabilize to quadcopter where it will better perform in flight and against a moderate wind. With the lifting propellers being so affected by wind currents, my thought is to increase the center of mass without degrading the lifting capability and sustained flight characteristics.

Any thoughts on this will be greatly appreciated.